﻿270 Ni:i'FlR()XAIAS 



Male shell either rounded or broadly subhianjijulate behind, 

 often obliquely subtruncate above, arcuate below. Female 

 shell with a well-developed marsu])ial swellinj:^, the ])osterior 

 point much more elevated than it is in the male. 



I,eng-th 60, heig-ht ^i^- <liam. 18 mm. 



Length 112, height 56, diam. 42.5 mm. 



Mexico. 

 Unio o.ztccoritni Phtmppi, Zeits. fiir Mai, I\', 1847, P- 05- 



Abbild., Ill, 1849, P- 100, pi. VI. fig. 2. — KusTER, Conch. 



Cab. Unio, 1862, pp. 2, 84, pi. xcv, fig. 6. — von Martens, 



Biol. Cent. Am., Moll., ifjoo, p_ 502, pis. xxxvi, figs. 2-4, 



xxxvii, figs. 3. 30, 3/7. 

 Margaron (Unio) aatecoruin LviA, Syn., 1870. p. 44. 

 Lampsilis actecorum Simpson, Syn.. 1900, p. 572. — Pilsrry,^ 



Pr. Ac. N. Sci. Phila.. 1909. p. 533. 



1 am a good deal in doubt as to this species, which I placed 

 in LauipsUis in the Synopsis. Philippi's figure is poor and it 

 probably represents a female. \'on Martens figures a number 

 of specimens, some of which agree fairly well with Philippi's 

 figure and others differ widely from it. If von Martens is 

 correct the species should go in Ncf'lirouaias, as the males are 

 arcuate below and sometimes biangulate behind, characters 

 which do not belong to Lampsilis. He is mistaken, I believe, 

 in referring the Unio strebelii I.ca to this species as a variety. 

 I am sure that it is a synonym of A^. medellina. Unio emariiin- 

 atiis Lea. which he seems to think may be asteconuii, is, I am 

 almost sure, a palearctic species. 



The larger dimensions given are for one of von Martens' 

 shells. 



Var. cliapolaniis von Martens. 



"Somewhat higher com])aratively. es]iecially in its hinder 

 part ; brownish-yellow, with some green rays ; ventral margin 

 scarcely concave ; cardinal teeth more feeble ; inside white. 



Length, 60. alt. vert. 31.5, al?e 32. diam. 20 mm. \'ertices 

 in 34 long." (von Martens.) 



Tvpe locality, Laguna de Chapala. Central Mexico. 



